This invention relates to olefin polymerization processes and the resultant polymer products.
Ultra high molecular weight olefin polymers such as polyethylene usually have excellent properties, such as, for example, high impact strength and dimensional stability, low coefficient of friction, self-lubricating and are highly resistant to most chemicals. Thus, ultrahigh molecular weight polyethylenes are useful in many demanding and extremely critical applications, such as human joint replacements, gears, bullet proof vests, skis, and other applications. However, ultrahigh molecular weight polyethylenes can be difficult to process with conventional equipment. Since ultra high molecular weight polymer cannot be pelletized after leaving the reactor, the polymer must be sold as a fluff or a powder. Therefore, particle size and toughness of the resultant polymer is critical.
Many commercial methods are available to produce olefin polymers, such as polyethylene. One of the most economical routes to most commercial grades of olefin polymers is a loop/slurry process with a paraffin diluent wherein the polymerization process can be carried out at a temperature low enough that the resulting polymer is largely insoluble in the diluent. It is believed that commercially acceptable ultra high molecular weight ethylene polymers traditionally are made using a stirred tank process, in a heavy hydrocarbon diluent.
It is an object of this invention to provide very tough ultra high molecular weight homopolymers of ethylene and copolymers of ethylene/1-hexene.
It is another object of this invention to provide ultra high molecular weight ethylene/1-hexene copolymers having improved physical properties compared to conventional ultra high molecular weight ethylene homopolymers.
It is a further object of this invention to provide an improved olefin polymerization process which can produce both homopolymers of ethylene and copolymers of ethylene and at least one other higher alpha-olefin comonomer.
It is yet another object of this invention to provide an improved polymerization process for preparing ultra high molecular weight polyethylene.
It is a further object of this invention to provide an improved olefin polymerization process which can produce copolymers of ethylene and at least one other higher alpha-olefin comonomer using a catalyst system selected from the group comprising supported Ziegler-Natta catalyst systems, organo-zirconium catalyst systems and organo-hafnium catalyst systems.
It is a further object of this invention to provide an improved olefin polymerization process which can produce homopolymers of ethylene using a catalyst system selected from the group comprising organo-zirconium catalyst systems and organo-hafnium catalyst systems.
In accordance with one embodiment of this invention, a process is provided which comprises polymerizing ethylene in a loop/slurry process using a catalyst system selected from the group comprising supported Ziegler-Natta catalyst systems, organo-zirconium catalyst systems and organo-hafnium catalyst systems to produce very tough ultra high molecular weight copolymers of ethylene and at least one other higher alpha-olefin comonomer.
In accordance with another embodiment of this invention, a process is provided which comprises polymerizing ethylene in a loop/slurry process using a catalyst system selected from the group comprising supported organo-zirconium catalyst systems and organo-hafnium catalyst systems to produce very tough ultra high molecular weight homopolymers of ethylene.
In accordance with still another embodiment of this invention, a process is provided which consists essentially of polymerizing ethylene in a loop/slurry process using a catalyst system selected from the group comprising supported Ziegler-Natta catalyst systems, organo-zirconium catalyst systems and organo-hafnium catalyst systems to produce very tough ultra high molecular weight copolymers of ethylene and at least one other higher alpha-olefin comonomer.
In accordance with still another embodiment of this invention, a process is provided which consists essentially of polymerizing ethylene in a loop/slurry process using a catalyst system selected from the group comprising supported organo-zirconium catalyst systems and organo-hafnium catalyst systems to produce very tough ultra high molecular weight homopolymers of ethylene.
In accordance with yet another embodiment of this invention, a composition comprising a very tough, ultra high molecular weight polyethylene is provided.